All-weather projectile fire control system-director mode



Apr1127, 1965 J. A. cRAwFoRD r-:rAL 3,181,147 I Y ALLWEATHER PROJECTILEFIRE CONTROL SYSTEM -vDIRECTOR MODE Filed March 15, 1962 3 Sheets-Sheet1 @Wkbbfbb Aprll 27, 1965 l 3,181,147

ALL-WEATHER PRoJEc'rILE FIRECONTROL SYSTEM DIRECTOR MODE J A. CRAWFORDETAL 3 Sheets-Sheet 2 Filed umhv 15, 1962l INV ENTOR. JA CA A. CPA WFODJH/V H. GREGORY Apr1l27. 1965 J. A. CRAWFORD HAL 3,181,147

ALL-WEATHER PROJECTILE FIRE CONTROL SYSTEM DIRECTOR MODE Fi1ed Harch 15,1962 3 Sheets-Sheet 3 United States Patent C) 3,181,147 ALL-WEATHERPRUJECTILE 11H-lll CNTRL SYSTEM-DCTUR MODE lack A. Crawford and .lohn H.Gregory, Qlrina Lake, Calif., assignors to the United States ofAmericaas represented hy the Secretary ofthe Navy Filed Mar. 1S, 1962, Ser. No.181,229 9 Claims. (Cl. 343-7) (Granted under Title 35, U.S. Code (1952),sec. 266) The invention described herein may be manufactured and used byor for the Government of the United States of America for governmentalpurposes without the payment of any royalties thereon or therefor.

This is a continuation-in-part of our patent application Serial Number673,748, filed July 23, 1957, for All- V/eather Projectile Fire ControlSystem-Director Mode, now abandoned.

This invention relates to an all-weather projectile tire control systemfor vehicles,V as aircraft or-the like, for computing projectile tirecontrol problems and for displaying resulting projectile firing leadangles on a cathode ray tube and on a sight unit to enable tiringpersonnel to effect projectile and target collision although either thevehicle, or the target, or both, are moving. More particularly, theinvention relates to a circuit in the al1- Weather projectile re controlsystem for feeding back signal information between predetermined pointsof the computing circuits to decrease or speed up the response time ofcomputation of the resulting lead angles thereby giving instantaneousand continuous displays of the lead `angles for projectile and targetcollision to eliminate overcorrection of the lead angle by operatingpersonnel.

In the projectile fire control problem, computations are necessary foreffective projectile tire on moving targets, and particularly where boththe target and the nre control system are moving as, for example, in thesituation of pursuit and target aircrafts. The lire control problem maybe compared with that of a hunter wherein the hunter must attempt tomentally compute a lead angle for his gun to hit a flying bird. Thehunter must compensate for gravity effect, bird direction and speed,wind direction, range, bullet speed, etc., in order to ensure a hit. Thehunter cannot expect to hit a ilying bird by aiming directly at it. Thehunter must learn to lead or aim ahead of the bird so that the bird andshot will collide with each other. The greater distances between pursuitaircraft and target aircraft in combat require solution by scientificmeans since man is incapable of solving these problems while understress of self preservation and in the short space of time often timesdemanded in combat. The problem is further complicated by the conditionthat the pursuit aircraft is also moving which necessitates the solutionto find the kinematic lead angle or the angle of offset necessarybecause of the relative motion of the pursuit and target ail-crafts.This invention is therefore directed to the improvement of solving thelead angles for fire control problems in Va substantially instantaneousand continuous manner.

The present invention is a modification of the allweather gun tirecontrol system shown and described in the patent application of E. FrankEcholds, Serial Number 848,873, tiled October 26, V1959, which is acontinuation-in-part application of Serial Number 585,589, led May 17,1956, for an Airborne Fire Control System, both applications nowabandoned. The combination of the all-weather gun re control system ofthe abovementioned application is the basic combination of the presentinvention. The eddy-current gyroscope shown and described as a componentin the present disclosure CII is fully shown and described in the patentof E. Frank A, altari Patented Apr. 27, 1965 ICC Echolds and Paul L.Brink, bearing the Patent Number 2,960,825 which issued August 25, 1959,for an Eddy- Current Force System for Constrained Gyroscopes.

In the application of E. Frank Echolds, Serial Number 848,873, a radardevice is used to seek outtargets and, when one is found, the devicewill develop azimuth and elevation information signals which aretransmitted by self-synchronous transmitters to circuits for use. Theradar device also develops range information signals that are passedthrough computing means to provide range rate signal information whichrange and range rate signal information, together with signalinformation of factors pertinent to the solution of a gun fire or rocketcontrol problem, are computed into range currents and deflectioncurrents for a lead computing or eddy-current constrained gyroscope. Therange and deflection currents actuate the eddy-current gyroscope to aprocessed equilibrium position which position is sensed by aselfsynchronous transmitter for each gyroscope gimbal axis. Theseself-synchronous transmitter signals, representative of lead angles inazimuth and elevation computed to cause projectile-target collision, aremixed in a difference circuit to which the azimuth and elevationinformation signals of the radar are applied to provide resulting errorinformation signals. These error information signals are demodulated andapplied to a cathode ray tube for display of the error ofprojectile-target collision.` The use of the term projectile hereinrefers to gun missiles, rockets, or other types of projectiles that maybe tired. By proper maneuvering of the vehicle the error can be reducedto zero at which time the guns or rockets may be iired andprojectile-target collision assured. Some time must be allowed, however,after maneuvering the vehicle, to allow for computations to be made anda corrected error signal displayed. This system also anticipates the iinclusion in the combination of a sight unit which is coupled to thecomputing circuitry to display fixed and movable reticles showing thegun reference line and the lead angle, respectively. The sight unit maybe used when .the target is visible to vehicle personnel.

In the present invention a circuit modification or addition is made tothe all-Weather gun iire control system which produces a rapid responseof the computing circuitry so that gunnery personnel can maneuver thegun reference line rapidly to the zero error position by actualobservance of the display on the scope or sight unit; that is, insteadof mentally estimating the maneuvering necessary to correct the error inlead angle and awaiting confirmation by the computing circuits, thevehicle personnel can maneuver the vehicle to constantly reduce theerror signal to zero by observance of the display on the cathode raytube or the sight unit. The instantaneous visual display is accomplishedby feeding back the output of the difference circuit to the eddy-currentgyroscope to produce gyroscope output signal information to thedifference circuit approaching the actual lead angle determined by theradar. This instantaneous visual display, by which operating personnelcan maneuver the vehicle to reduce the error of the lead angle to zerofor proper projectile-target collision, is considered herein as thedirector mode of operating the all-weather projectile fire controlsystem. The sight unit may be operated as before or it may be coupled inthe modied circuit to provide instantaneous movable reticle positions inthe same manner as on the cathode ray tube screen. The present inventionenables operating personnel to watch lthe results of their maneuveringof the vehicle into position for effecting projectile-target collisionWithout hesitation. It is therefore an object of this invention toprovide an all- Weather projectile lire control system for a Vehiclewhich produces instantaneous and continuous visual indications sprain/i7D of the error of lead angle on a target to enable operating personnelto rapidly maneuver the vehicle for projectile collision with lthetarget Whether the target is v1sible or invisible.

These and other objects, advantages, features and uses will become moreapparent as the description proceeds when considered along with thedrawing, in which:

FIGURE 1 illustrates in block diagram the flow of signal information forthe all-weather gun fire control system, director mode; k

FIGURE 2 illustrates a modification of this gun fire control system,director mode;

FIGURE 3 illustrates a schematic wiring diagram of computer 21 ofFIGURES 1 and 2; and

FIGURE 4 illustrates a schematic wiring diagram of computer 20 ofFIGURES 1 and 2.

Referring more particularly to FIGURE l, there is shown a projectilelire control system which may he carried by a vehicle such as anaircraft, ship, or the like.

For the purpose of illustration and explanation of the invention, let itbe assumed that the fire control system is being carried by a lighteraircraft having fixed guns oriented with the gun lines parallel inalignment with the longitudinal center line of the aircraft and rocketlaunchers preset for proper angle of attack in the airstream from theaircraft. The lire control system includes a radar device having arotatable antenna 11 for seeking out targets. The radar 10 may be of anywell known automatic tracking type which produces signal informationoutputs of azimuth and elevation of any target detected. The azimuth andelevation signal information is transmitted over the functional leads 12and 13 to a difference circuit 14. The circuit 14 may be any differencecircuit for producing the difference in alternating current (AC.)signals, although a specifically designed difference circuit asdisclosed in the application, Serial Number 848,873, may be used. Theazimuth and elevation signal information is developed by resolverswithin the radar device to produce alternating current voltage signalsby way of self-synchronous transmitter means to produce specic fieldsrepresentative of the azimuth and elevation of the target. The radardevice 10 is also capable, as is well known, to produce a variabledirect current voltage signal by way of the functional lead 15representative of the target range. As is understood in the art, apredetermined number of yards may be represented as one volt in therange intelligence signal whereby the exact range from a known rangevoltage may be determined. The radar device 10 is preferably of the typetoset the antenna in a rotating search mode and to automatically switchto a tracking mode when a target appears whereby the antenna follows thetarget, as is well understood in the art of radar detection systems.

In addition to the radar detection system, the allweather fire controlsystem includes circuitry which utilizes the information derived fromthe radar to compute proper lead angles so that the guns or rockets ofthe aircraft, or the like, may be fired to cause projectile and targetcollision. In this all-Weather tire control system the range voltagesconducted by the functional lead 15 are applied in parallel to acomputer circuit and to a computer circuit 21. The computers 20 and 21will be described in detail in the description of FIGURES 3 and 4. 'Ihecomputer circuit 21 computes each range voltage into range rate or therate at which the target and the vehicle are closing. This range ratevoltage is also applied by the functional conductor 22 to the computercircuit 20. Several factors, which are necessary in making thecomputations of a fire control problem, are also applied to the computercircuit 20 and are shown in block diagram in FIGURES 1 and 2. Thefactors to` be considered are the ammunition data represented by theblock 23, the attack and skid angles represented by the block 24, theaccelerometer measurements represented by the block 25, the air densityrepresented by the block 26,

and the indicated air speed represented by the block 27. The ammunitiondata and the attack and skid angles may have voltage signals applied byWay of the functional conductors 28 and 29 which voltages are developedand manually adjustable as will be described more fully in thedescription of FIGURES 3 and 4. The settings of these two informationaldevices are different for bullets and rockets and it will be necessaryfor operating personnel to make the proper settings for the type ofprojectile used. The accelerometer, air density, and indicated air speedvoltage signals are usually developed from instrumentation in theaircraft and these voltage signals are automatically transmitted by wayof functional conductors 30, 31, and 32, to the computer circuit 20. Thecomputer circuit 20 accepts and utilizes the voltage signals of range,range rate, and the other abovementioned voltage information of factorsnecessary to solve the projectile tiring problem to produce signalinformation in currents representative of range, azimuth, and elevation.

The output current signal information of range is transmitted by thefunctional conductor 35 through a current amplifier 36 to the rangecoils of an eddy-current gyroscope 37. The deflection or offset currentsrepresentative of azimuth and elevation are transmitted by way of thefunctional leads 38 and 39 through the current amplifier 36 to theoffset or deflection coils of the eddycurrent gyroscope 37. Theeddy-current gyroscope with specific description of the range and offsetcoils is speciically shown and described in the aforementioned PatentNumber 2,900,825, of E. Frank Echolds and Paul L. Brink, and will not befurther described herein. The range signal currents transmitted by wayof the functional lead 35 are obtained in the computer circuit 29 bycomputation using primarily the range, range rate, indicated air speed,air density, and ammunition data Voltage signals. The elevationalcurrents transmitted by way of the functional conductors 39 arel derivedprimarily from voltage information of the accelerometer and the attackand skid angle devices, and from the range currents computed above. Thedeflection of offset currents for azimuth transmitted by Way of thefunctional conductors 38 are derived in the computer circuit 20primarily from the range voltage applied over the functional lead 15 andthe attack and skid angle voltage applied over the functional lead 29from the component 24. The range currents will produce a magnetic fieldin the eddy-current gyroscope range coils to cause a precessing forcewhich allows a finite lead angle to be produced by the aircraft, or thelike, whenever a turning rate is generated by maneuvering into aposition of gun or rocket tiring. The offset currents of azimuth andelevation presented by the lconductors 38 and 39, respectively, deflectthe gyroscope in the manner computed, together With the range currentinformation, to effect a lead angle necessary for gun or rocket tiringin accordance with the information submitted to the computer circuit 20by the functional leads 15 and 22 and the data devices 23 to 27,inclusive.

The deflection intelligence of the eddy-current gyroscope is provided byalternating current voltage signals transmitted by a self-synchronoustransmitter on each of the gimbaled axes of the eddy-current gyroscopeas is more fully shown and described in the aforementioned Patent Number2,900,825. These informational signals are transmitted by way of theconductors et? and 41 to the difference circuit 14. The informationsignals coming by way of the functional leads 40 and l1 arerepresentative of the computed lead angle to lire on a specific targetWhile the information signals coming by Way of the functional leads 12and 13 from the radar are representative of the actual lead angie orangle of deviation of the target from the gun lines of the aircraft. Thedifference of these two informational signals, that is of the azimuthand of the elevation, produces co-ordinate voltage signals on thefunctional output leads 42 and 43 which represent the error lead angleor the angle of error beth in azimuth and' elevation which the aircraftshould ily, when corrected, to bring the gun lines into position toeffectively cause projectile and target collision. These error voltagesignals are amplified in amplifier i5 and demodulated in theydemodulator 46 which may be of a phase sensitive rectifier type ltoproduce error voltage signals in azimuth and elevation suitable forapplication to the deflection circuits of a cathode ray tube 50. For adesirable presentation, a time-sharing circuit may be used in thecircuit between the demodulator lo and the cathode ray tube Si? topresent a plurality of informative signals on the screen 5l of thecathode ray tube. The time-sharing circuit i7 may be used to cause twosimultaneous displays on the screen Si of the cathode ray tube 5@ to aidoperating personnel in effectively firing on the target. The errorsignals coming from the difference circuit 14 will cause a fluorescentpip to be produced as a steering dot 52, and a second representationshown by a donut-shaped steering circle 53, which is usuallyapproximately one-fifth of the distance from the steering dot 52 to thecenter of the cathode ray tube screen Sl, may be created from the errorsignals at reduced amplitude. The screen 51 of the cathode ray tube Stimay be divided into quadrants by lines or by other grid means, asdesirable. The steering circle 53 is produced in any well-known mannerin the cathode ray tube electronics by applying vtwo sine wave voltagesin out-of-phase relation to the deflection circuits to produce thiscircular pattern commonly known as one of Lissajous figures. Asdescribed more fully in the above-mentioned patent application of theall-weather fire control system, the pilot or operating personnel needonly to maneuver the aircraft to reduce the lead error angle to zero atwhich time the steering dot 52 is within the steering circle 53 and bothare lying on the center of the cathode ray tube screen 5i, this centerrepresenting the gun line or longitudinal reference line of theaircraft.

As also more fully described in the aforementioned patent applicationSerial Number 848,873 of the allweather gun lire control system,information signals from the computer circuit 2) may likewise be appliedto a gyroscope sight unit 6i? which includes range coils and deflectionor offset coils in a constructional manner similar to that of theconstrained eddy-current gyroscope 37. rlhe range current informationwill be supplied by the functional lead 35 and the azimuth andelevational signal information will be supplied by the functional leads38 and 39. While the deflection or offset current signals are coupled toleads 38 and 39, respectively, prior to current amplifier 36, it may beunderstood that the current signals 38 and 39 may be taken subsequent tocurrent amplification, where desirable. The sight unit produces a fixedreticle and a movable reticle on a transparent plate 61 of the sightunit or the windshield of the aircraft as may be desired. As is wellunderstood of the sight unit, the fixed reticle represents the gun lineor longitudinal reference line of the aircraft whereas the movablereticle illustrates the lead angle for proper gun firing to causeprojectile-target collision. As more clearly described in theprior-mentioned application Serial Number 848,873, of the all-weathergun iire control system, operating personnel may actually view thetarget and get proper bearing by bringing the target to the center ofthe movable reticle. At the time the target is at the center of themovable reticle on the sight unit glass plate 6l, the steering dot andsteering circle should be concentric over the center of cathode ray tubescreen 5l.

The above description sets out briefly the combination and advantages ofthe all-weather gun iire control system fully shown and described in theprior-mentioned patent application Serial Number 848,873, for thatsystem. The description is repeated here to more fully provide a basisfor the circuit modification to make the all-weather gun fire controlsystem operate in the director mode which E? is the subject matterspecically of the present invention. The present invention contemplatesfeeding back the error azimuth and elevation signals transmitted by wayof the functional conductors 42 and i3 on functional conductors 65 and66 through a power amplifier 67 and a demodulator d8 to impress thisazimuthal and elevational error voltage signal information on thedeflection or offset currents applied to the azimuthal and elevationaloffset coils of the eddy-current gyroscope 37. The azimuth signal comingby way of the functional conductors 12., 42, and 65, is applied by thefunctional conductors 69 to the deflection or odset azimuth currents inthe conductors 3S. Likewise, theelevation signal information coming byway of the functional leads 13, 43, and 66, is applied by the functionalleads 76 to the elevational deflection or offset currents in thefunctional leads 39. While it is shown and described that the azimuthaland elevational feedback voltages applied by way of 69 and "i0,respectively, are coupled to the functional conductors 38 and 39 in thecurrent amplifier 36, it is to be understood that lthis coupling may bemade before or after the current amplifier with suitable results, itonly being necessary to apply these error signals through isolatingmeans as is well understood in the art. Four leads, that is, two leads38, two loads 39, two leads 69, and two leads 78, are shown since theapplication of the currents to the deflection or offset coils of thegyroscope 37 is arranged to be additive in one offset coil andsubtract-ive in the companion offset coil for each azimuthal orelevational plane, as better understood from the description in thepriormentioned Patent Number 2,908,825 and application Serial Number848,873 of the all-weather iire control system. Since the application ofthe azimuthal and elevational voltages in o9 and 7i) is applied tosubstantially zero impedance circuits, the addition or subtraction ofthe feedback is equivalent to current feedback which decreases theoffset of the eddy-current gyroscope to produce output informationsignals on the informational conductors til and 4l to more nearlycorrespond to the actual information signals coming from the radar byway of the functional conductors l2 and f3. This, in effect, produces amuch more rapid response of computation which will be displayed upon thecathode ray tube screen 51 so that operating personnel can actuallywatch the maneuvering of their aircraft by the instantaneous andcontinuous response of the error lead angles represented by the steeringdot 52 and steering circle 53. Without the benefit of the feedbackcircuit of this invention, operating personnel could only maneuver theaircraft to a position of orientation as a result of guessing thecorrection needed from the display shown and then wait to see if theirnew orientation was correct by watching the results of computations bythe positioning of the steering dot and steering circle. By use of thisinvention, including the feedback circuit, the steering dot and steeringcircle would immediately respond to display the moving of the aircraftwhereby aircraft personnel could readily and instantaneously determinewhen the error lead angle became zero at which time the aircraft wouldbein position to effect projectile-target collision. lt may be noted thatin this illustrated combination the feedback circuit would not disturbthe results produced by the sight unit dil but only decrease theresponse time for the display on the cathode ray tube which cathode raytube display is used by operating personnel for unseen targets as whenthe target is concealed by inclement weather', darkness, smokescreen, orthe like.

Referring more particularly to FIGURE 2, the same basic all-weather firecontrol system combination of components is used as shown and describedfor FIGURE 1 and these components bear like reference characters withthose of the corresponding components of FIGURE 1. In this modificationa sight unit is used which is controlled by a self-synchronous orsynchro motive means to position the movable reticle for azimuth andelevation.

adelaar The sight unit 75 casts fixed and movable reticles on thetransparent' plate 61 or Windshield of the aircraft in the same manneras described for the sight unit 60 of FIGURE l. The selfsynchronousreceivers of the sight unit '75 receive signal information from theradar 10, taking the information from the functional conductors 12 and13 for the azimuthal and elevational information signais, respectively,over the functional conductors '76 and 77 to an adding circuit 78. Afeedback from the difference circuit 14 by way of the functional leads42 and i3 is also applied to the adding circuit by way of the functionalleads 79 and Sti. The difference of the actual azimuth and elevation isadded to or subtracted from the error signais coming by way of thefeedback to produce resulting self-synchronous or synchro signals overthe functional conductors S1 and S2 to the sight unit 75. By thisconstruction it may be readily realized thatthe sight unit '7S willoperate in the director mode the same as the director mode operation forthe cathode ray tube t?. in this manner the operating personnel willredirect the aircraft to bring the steering dot 52 on the cathode raytube S1 Within the steering circle 53 overlayingV the axis of thecathode ray tube 5d which, at the sante time, will bring the movablereticle on the glass plate 61 to be superimposed over the target withequal rapidity. In the prior case where operating personnel redirect theaircraft for iire control on an unseen target the cathode ray tube 5? isused, but in the latter instance the sight unit is used for visibletargets. The construction of FIGURE 2 has an advantage for operatingpersonnel in that the displays on the cathode ray tube screen and on thesight unit glass plate are of equal speed in showing the correctioncarused by maneuvering.

While the computers 20 and 21 may be of any type to produce the outputcurrents in range, azimuth, and elevation for the eddy-current gyroscope37, the computers used in the basic all-weather iire control system ofthe above-mentioned patent application, Serial Number 848,873, will beshown and described herein for convenience in understanding theinvention. Referring more particularly to FIGURE 3, where computer Z1 isillustrated in broken lines, the radar range input signal coming by wayof conductor 15 is applied to the grid of the vacuum tube section 1G1A.This is a cathode follower circuit and its purpose is to reproduce theinput signal with negligible loading on the input circuit. The output ofthe cathode follower circuit is connected through a resistor 102 and adifferentiating capaci-tor 103 to the grid of the amplifier tube section1MB. Negative feedback from the cathode of an output tube 16d throughresistors 1115 and 106 is also applied to the grid of tube section 101B,the resistor 1115 being adjustable. Capacitor 1017 with resistor 102forms a filter circuit which tends to attenuate any extraneous highfrequency inputs arising from noise pickup, hum, power supply ripple, etcetera, which may be present in the radar input signal.

The output of the amplifier 101B is connected through the circuitconsist-ing of resistor 16S and capacitor 109 to the grids of the outputtube 164. Capacitor 11i-9 allows high frequencies, which are not stoppedby resistance 102 and capacitor 11W, to pass. Tube 1554 is a cathodefollower which reproduces its input signal.

Resistors 1110, 111, and 108, form a voltage divider which establishesthe anode voltage for tube section 101B and the grid voltage for tube104. Resistors 113, 114, and 11S, form a biasing circuit for the cathodeof tube section 161B. The resistor 114 is variable and is used to beadjusted so that with zero input to the grid of tube section 191B therewill be a zero potential at the cathode of tube 184. The presence of theresistance 115' cau-ses a degenerative process which reduces the eectivegain of the amplifier. This effect is eliminated by connecting theresistance 116 from the cathode of the output tube 104 to the cathode ofthe amplifier tube section 1MB. This produces a regenerative effect andthe value of resistance ci 116 is chosen to overeompensate, thusproducing a net increase in gain.

The output slope factor is determined primarily by the value of thedifferentiating capacitor 163 and the resistors 1115 and 1% since forany given range-rate the charging current depends on the value of thisresistance. The accuracy and stability of the unit depends to'a greatextent on these components. The differentiating capacitor 1li/i3 musthave negligible leakage over the entire range of operating temperatures.Accurate adjustment of the slope factor is made by adjusting thevariable resistance 1115.

Neon tube 117 permits quick recovery from overloading. Since all changesin range-volts input appear on the grid of tube section 101B, thecircuit may overload since only a limited charging current is availablethrough the resistance 1%. A very rapid decrease in range could resultin large negative voltages at the grid of tube sect-ion 191B and thecomputer might become inoperative for several seconds except for thepresence of the neon tube 117 which breaks down during a negativeoverload and provides a low impedance path enabling the capacitor 103 tocharge quickly to the required voltage. Other resistances in the circuitnot particularly identified by reference character establish biasingVvoltages for the amplifier and output tubes in a manner well understoodin the art and will. not therefore be specifically described.

With the operating voltages placed on the circuitry, as illustrated inFlGURE 3, let it be assumed that a constant range-volts input signalexists on input 15. The grid of the amplifier 101B and the cathode ofthe output tube 19d will then be at zero potential. Now assume that therange voltage decreases (range voltage is always positive). The cathodeof tube section 1i1A becomes negative and the differentiating capacitor1513 discharges through resistances and 196. The rate at which thiscapacitor discharges is proportional to the rate of change of the'applied voltage or, mathematically speaking, it is proportional to thederivative of the applied voltage. Thus a negative voltage proportionalto the rate of change of the input signal is applied to the grid of theamplifier tube section 101B. Current flow through tube section 101Bdecreases, causing the anode of tube section 101B and the grids of tube101i to become more positive. This causes the current iiow through tube104 to increase and the cathode of this tube to become positive. Thepotential at the cathode of tube 104 is the range-rate signal conductedto the output thereof over a conductor 22. It is also fed back to thegrid of the amplifier, thus decreasing the initial effect of thepositive voltage. The rangerate out signal is positive for decreasingrange signals on the input 15 and negative for increasing range signalson the input 15, and proportional to the rate at which range ischanging.

Referring to FIGURE 4, the computer shown in block by the referencecharacter 2i? in FIGURES 1 and 2 is included within the block enclosedby broken lines in this figure. The inputs 23 to 27, inclusive, areshown within dotted lines outside the main block 20 with the circuitrywithin these small blocked areas representative of the general circuitmeans for developing the respective input signals to the computer 20.The computer 20 is shown partly in block diagram and partly in circuitdiagram with functional leads having arrows thereon representative ofthe direction that information is traveling through the computer toprovide the three-output informational intelligence of elevationalcurrents, range currents, and azimuthal currents for the lead computinggyroscope 37. The computer utilizes a number of phase-balance computers,which are referred to herein as PBC-1, PBC-2, et cetera, by legendsthereon in preference to reference characters since it is believed suchidentification will make the diagram of this computer more readilyunderstandable. As is well understood in the art, phasebalance computershave magnetic amplifiers therein which make them readily adaptable foruse as multipliers, in-

verters, dividers, summing circuits, or square root calculators,depending on the manner in which they are connected. The phase-balancecomputers used herein are of the type shown and described in UnitedStates Patent Number 2,733,004, of John E. Richardson, entitledElectrical Computers, and in the United States Patent Number 2,870,960,of John E. Richardson, entitled System for Analog Computing UtilizingDetectors and Modulators.

The range signal coming by way of the functional lead is applied to thephase-balance computer, PBC-1, and the range rate signal coming by wayof the functional lead 22 from the computer 21 is applied to PBC-2.PBC-1 and PBC-2 are coupled and operated as directcurrent toalternating-current (D.C. to A.C.) inverters. The output of PBC-1 isapplied through the functional lead 125 to the PBC-3 which is circulatedto operate as a divider circuit. The output of PBC2 is coupled to a'transformer 126 in a transformer unit 127 through a primary winding,which primary winding is also coupled by functional lead 12S coming fromthe ammunition data input 23. The information coming from the ammunitiondata means 23 is the average velocity of the projectile used, as will bemore fully described'later, which average velocity represented by anA.C. voltage signal is summed with the A.C. voltage signal, or rangerate signal, from PBC-2. The summed average velocity and range rate A.C.voltage signals are applied from the secondary of transformer 126through the functional lead 129 to PBO-3 where division of the range bythe sum of average velocity and range rate is accomplished to produce atime of flight A.C. voltage signal on the output conductor means 130.The time of flight signal is rectified in the linear rectier and appliedto a magnetic amplifier over functional lead 131 as a D.C. voltagesignal where it is summed with the D.C.' signal applied over conductormeans 32 from the air speed input 27. While the air speed signal isdeveloped from one of three D C. signals representative of theaircraftrspeed, either as low, medium, or high speeds, shown herein bythe taps designated as L, M, and H, it is to be understood that this airspeed signal may be developed by potentiometer or other means which isinstrument actuated. The summed D C. components are multiplied by theair density factor coming from the air density block 26. This isrepresented as having the output of the magnetic amplifier on thefunctional lead 133 as passing through a potentiometer to PBC-4, thelatter of which is a D C. to A.C. inverter. The potentiometer of the airdensity block 26 is illustrated as being instrument actuated to clarifythe manner in which this multiplication factor, or proportional factor,is provided. The output of PBC-4 is applied by way of functional lead134 to two coils 135 and 136 in the ammunition data device 23. Each coilis tapped at a point providing an A.C. output representative of theaverage muzzle velocity factor for guns or the burnt-velocity factor forrockets which result in an output of the average velocity. For thepurpose of illustration, the coil 135 is tapped by a functional lead 137to a switch contact identified by the letter G which is representativeof the ammunition data for guns. The coil 13d is tapped at a pointrepresentative in A.C. voltage signal of the burnt-velocity factor forrockets which is conducted by the functional lead 138 to the switchcontact, herein designated by the letter R. The switch gang 141m of acomposite switch is shown in position on the gun tap G to provide theaverage velocity for gun projectiles over the conductor means 125 which,as hereinbefore stated, is applied to one end of the transformer primary126.

PBC-5 is arranged to produce multiplication. To lBC5 is applied the A.C.time of flight voltage signal coming from the output 130 of PBC-3through the functional lead 145 and a portion of a transformer winding146 which is tapped by the functional lead 147 to PBC-5. The tap on thewinding 146 is at a point representing a constant, equivalent to 1/2times gravity, whereby the multiplication takes -place in this winding146, applying the product over the functional lead 1417 to PBC-5. Theother multiplication factor is an A.C. current representative of therange current produced as an output of PBC-3, hereinafter more fullydescribed, over the functional lead 148 to PBCS. This range current fromfunctional lead 143 is also applied to a transformer winding 149 by atap thereon, the winding of which has an output 35 being the rangecurrent applied to the range coils of the lead computing gyroscope 37.The output of PBC-5 is applied by the functional lead 151) to PBC-6,which is connected as a divider. The output of PBC-5 is an A.C. voltagesignal representative of the product of 1/z gravity times the time offlight which is equivalent to the product of the average velocity timesthe gravity drop angle. This product coming by way of functional lead150 is divided by the average velocity A.C. voltage signal coming by wayof functional lead 12S which is applied by the functional lead 151 toPBC-6 producing on the output functional lead 152 the product of rangecurrent and the gravity drop angle. This output is multiplied by thevoltage signal of the accelerorneter 25, illustrated herein as aninstrument actuated potentiometer. The output of the accelerorneter iscoupled to the switch blade of the switch gang 14u!) and is shown hereinas being connected to the gun tap G which applies this voltage signalthrough the functional leads 153 and 154 to the primary winding of atransformer'155. The secondary of transformer 155 transmits this voltagesignal by way of the functional lead 39 to the elevational control coilsin the lead computing gyroscope 37. In order to produce the rangecurrent on the output 14S of PBC8, the average velocity coming by wayofthe functional lead 128 from the ammunition data means 23 is appliedby the functional lead 161i to PBC-'7, which average velocity is dividedby the range signal coming by way of functional lead 161 which is tappedon the output functional lead of PBC-1. PBC-7 produces a time factorsignal on the output 162 applied to PBC-8 where the square root of thistime factor signal is taken to produce the range current.

The azimuthal currents for rockets applied on the output functional lead38 come by way of the switch gang 14110 and the functional lead 156 fromthe skid angle instrument represented by 24 in FIGURES 1 and 2. Thegeneration of an A.C. signal is illustrated herein merely as aninstrument actuated potentiometer to which is applied a predeterminedA.C. voltage. Since all of the outputs of thefcomputer 2f) are A.C.signals, these signals are rectified to D.C. currents by the rectifiermeans 157 which, for the purpose of simplicity, is shown as being withinthe computer 2t) herein.

In the case of rocket firing, the angle of attack of the aircraftcarrying the subject matter of the invention must be added to the outputsignal of the accelerorneter 25, which summed A.C. signal is applied byway of functional lead 154 to the primary of the transformer 155 toproduce the proper elevational currents for such rocket firing. Also forrocket firing the skid angle signal is used and is therefore switched inby the switch gang 140C to skid angle element 24, thereby providing theproper azimuthal currents for'rocket firing. For gun firing, switch gang1413erests on G, which G contact is coupled to an A.C. voltage source ofpredetermined amplitude. The composite switch gangs 141m, 140i), and140C have the two positions for gun and rocket firing, these positionsbeing represented on the switch contacts as G and R, respectively. Theswitch gang 14th: switches in the proper winding or 136 to introduce theproper muzzle velocity factor or burnt-velocity factor for averagevelocity; the switch gang 146i; switches in the attack angle signal forrockets and bypasses the attack angle signal for guns; and the switchgang 149e switches the skid angle signal out for guns and in forrockets.

The computer 2t? therefore receives the range signals from the automatictracking radar 1flover functional lead i l 15 and the range rate signalsfrom the computer 2 over the functional lead 22 together with the inputsignals coming from the elements 23 to 27, inclusive, to compute all ofthese input signals into the range currents, elevational currents, andazimuthal currents, produced on the outputs 35, 39, and 3S,respectively, for the lead computing gyroscope 37.

The operation of the computers 2i) and 2l is believed to be clear andapparent from the description of FIG- URES 3 and 4together with theiroperative relation in tbe all-weather re control system. Operatingprocedures heretofore included to describe the all-weather lire controlsystem, director mode, are believed to be clear but a brief descriptionof operation will be given for the purpose of clarity. The radar l beingof the automatic tracking type will become fixed on a target thereby toproduce range, azimuth, and elevation signals as hereinbefore disclosed.If the target is invisible to the operating personnel for the reason ofcloud formation, darkness, or otherwise, the operating personnel willwatch the display on the cathode ray tube screen 5l in either embodimentof FlGURE l or FIGURE 2. The steering dot and steering circle willdisplay the relative position of the target and the reference line ofthe aircraft embodying this fire control system and operating personnelwill redirect the aircraft to reduce the error signal for lire controlto zero. That is, by redirecting the aircraft to cause the steering dotand steering'circle to approach and ultimately be superimposed over theaxis of the cathode ray tube screen, the error for projectile and targetcollision is reduced to zero. The steering circle 53 gives a coarseindication of target position while the steering dot 52 is a Vernierindication of error of target position. ln the director mode of thislire control system, operating personnel can view instantaneously theresults of their aircraft redirection by the display on the screen 5lthus avoiding overshooting or overcorrection. When the error signal isreduced to zero, the gun projectile or rocket may be red with theassurance of projectile-target collision since all computations of thefire control problem have been computed as hereinabove shown anddescribed and these computed results are accounted for on the screen Silpresentation unless errors have been introduced by manual adjustment ofthe ammunition data device 23 or attack and skid angle device 24 or bysome error of the elements 25, 26, or 27, which caused the computer 2lito produce erroneous range, azimuth, or elevation current signals to beapplied to the eddy-current gyroscope 37. It is a natural thing foroperating personnel, as the pilot or gunners, to direct the guns orrockets toward visual targets utilizing equipment necessary to solve thelead angle for projectiletarget collision. Where the target is visible,operating personnel will, in all probability, utilize the sight unit 60or 75 to effect this projectile-target collision. In the operation ofthe sight unit of FIGURE l, operating personnelwill redirect theaircraft to superimpose the movable reticle over the visible targetbefore firing. Since the sight unit 6i) is not operating under thedirector-mode, some delay may be experienced in awaiting changes of themovable reticle on the sight unit. Where time is of the essence,operating personnel may refer to the cathode ray tube screenoccasionally to see that they do not overshoot or overcorrect theredirection of the aircraft for proper projectile-target collision. Thesight unit in FIG- URE 2 is operating under the director mode and wherethe target is visible there is no necessity for the operating personnelto view both the glass plate 6l and screen 51 since there should be noovershooting or overcorrection by following the movable reticle andsuperimposing it over the target. The movable reticle will giveinstantaneous and continuous indications of lead angle forprojectile-target collision, the same as the indications on the screen5l. This enables the operating personnel to get a x on a target and tofire the projectile for target destruction in the minimum of timewithout fear of overshooting or overcorrection of the lead angle. Wherethe target may be visible part of the time and invisible part of thetime, as by the target passing through cloud formations or smokescreens,operating personnel may watch both displays of the cathode ray tube andthe sight unit to effect projectile-target collision. The location ofthe cathode ray tube and the sight unit should be such that operatingpersonnel should not have to make any substantial head or eye movementin viewing these two visible displays.

While many modifications and changes may be made in the constructionaldetails and the operation of the system, it is to be understood that thetwo embodiments herein are illustrative of the preferred forms of theinvention and are not intended to limit the invention except that it belimited only by the appended claims.

We claim:

l. In an all-weather projectile tire control system having a radartarget detection means providing actual azimuth, elevation, and rangesignal information with respect to a reference line, the actual azimuthand elevation Signal information being conducted through one circuit tothe deflection circuits of a cathode ray tube to prov-ide actual azimuthand velevation signal information for the cathode ray tube co-ordinatedisplay, and the range signal information together With signalinfomation representing factors affecting projectile trajectory beingconducted to computing circu-its for computing said range and factorinformation into computed range, azimuth, and elevation signalinformation with respect to said reference line, said computed range,azimuth, and elevation signal information being applied to aneddy-current constrained gyroscope to produce lead angle azimuth andelevation information signals, said lead angle azimuth and elevationalsignal information being applied to said one circuit to modify saidactual azimuth and elevational signal information t-o error lead angleazimuth and elevation information signals for co-ordinate display on thecathode ray tube to show the lead angle enror between said referenceline and the target, the invention which comprises:

a feedback circuit coupling each error lead angle azimuth and elevationinformation signal from points in said one circuit between saidapplication of said lead angle azimuth and elevation information signalsand said cathode ray tube to points in said coupling between saidcomputer and said eddy-current gyroscope to apply same to the respectivecomputed azimuth and elevation information signals thereby adjustingsaid error lead angle azimuth and elevation information signals toprovide instantaneous display on said cathode ray tube all relativemovements of the target and the fire control system. v

2. In an all-weather projectile tire control system having a radartarget detection means providing actual azimuth, elevation, and rangesignal information with respect to a reference line, the actual azimuthand elevation signal information being applied to a difference circuitthe output of which is through a demodulator providing actual azimuthand elevation signal information applied to the deflection circuits of acathode ray tube, the range signal information, together with signalinfomation representing factors to effect projectile and targetcollision, being conducted to computing means for producing computedazimuth and elevation signal information on the output thereof withrespect to said reference line calculated to effect projectile targetcollision, this computed azimuth and elevation information output beingapplied to an eddy-current constrained gyroscope to produce lead angleazimuth and elevation information signals, said lead angle azimuth andelevation signal information being applied to the difference circuit .tomodify said actual azimuth and elevation signal information to produceerror azimuth and elevation signal information for display on thecathode ray tube, and a sight unit coupled to receive the computedazimuth and elevation signal information for positioning a sightingreticle, the invention which comprises:

a feedback circuit coupling points between the difference and toposition the sighting reticle of the sight unit in response to computedazimuth and elevation information signals whereby a continuous displayand rapid signal response of .the misalignment of the target from saidrefe-rence line for projectile fire control to effect projectile andtarget collision is presented on said cathode ray tube and whereby acontinuous display and slow signal response of the roisalignment of thetarget from said reference line for projectile fire control to effectprojectile and target collision is presented on said sight unit.

3. In an all-weather gun fire control system as set forth in claim 2wherein said feedback circuit coupling a point between said differencecircuit and said cathode ray tube is between said difference circuit andsaid dernodulator.

4. In an all-Weather gun fire control system as set forth in claim V3wherein said feedback circuit includes an amplifier and a demodulator inseries to demodulate the error azimuth and elevation signal informationapplied to the eddy-current constrained gyroscope.

5. In an all-weatherprojectile tire control system having a radar targetdetection means providing actual azimuth,

elevation, and range signal information, the actual azimuth landelevation signal information-being applied to a difference circuit theoutput of which is fed through a demodu-lator to a cathode ray tubeproviding signal information forj actual azimuth and elevationcoaordinate voltages for target display, the range signal informationtogether with signal` information representing factors affectingprojectile trajectory for projectile-targetcollision being applied tocomputing circuits to produce computed azimuth and elevation signalinformation to effect target hit by the projectile which computedazimut-h and elevation signal information lis applied to the differencecircuit for producing error azimuth and elevation signal information todisplay on the cathode ray tube, and the first-mentioned actual azimuthand elevation signal information being coupled to a sight unit forpositioning a sight reticle for effective gun firing on a visibletarget, the cathode ray tube and the sight unit providing informationfor the liring of a projectile to effect projectile and target collisionof visible and invisible targets, the invention which comprises:

a feedback circuit coupling the output of the difference circuit withthe output of the computing circuits and with the coupling of the actualazimuth and elevation signal information to the sight unit for applyingthe error azimuth and elevation sign-al information respectively to thecomputed azimuth and elevation signal information and respectively tothe actual azimuth and elevation signal information to the sight unitwhereby signal response is rapid to display relative movements of thefire control system with respect to the target.

6. In a re control system as set forth in claim 5 wherein said feedbackcircuit coupling the output of said difference circuit with the outputof said computing circuits includes an amplifier and a demodulator inseries.

7. In a fire control system as set forth in claim 6 wherein saidfeedback circuit coupling the output of said difference circuit with theoutput of said computing circuits is through a low impedance coupling.

8. In an all-weather projectile lire control system for target pursuitvehicles providing a director mode of operation comprising:

a radar target detection device for providing actual azimuth, elevation,.and range information signals of a detected target;

a'demodulator and a cathode ray tube;

a difference circuit coupled to receive the actual azimuth and elevationinformation signals from the radar device, having the output thereofcoupled throughsaid demodulator to the deflection circuits of saidcathode ray tube for displaying error lead angles for correction toeffect projectile-target collision;

devices representing factors affecting projectile trajectory computercircuits coupled to receive the lactual rangel signal information fromsaid radar device and v-oltage signal information from said devicesrepresenting factors affecting projectile trajectory to produce rangecurrent signal information and computed azimuth and elevation currentsignal information representative of the lead angle for firing aprojectile at the target; an eddy-current constrained gyroscope coupledto receive said current signals for producing computed azimuth andelevation voltagesignal information of the lead angle coupled to saiddifference circuit, the difference in the Vactual azimuth and elevationsignal information from said radar and said computed azimuth andelevation signal information respectively producing azimuth andelevation error signals of lead angles for said display on said cathoderay tube;

and a feedback circuit coupling the azimuth and elevation error signalsof lead angle to therespective computed azimuth and elevation couplingsfrom said computing circuits to said eddy-current constrained gyroscopeto apply said azimuth and elevation error signals of lead angle,respectively, to said computed azimuth and elevation current signalinformation whereby the error signals of lead angles are rapidlycomputed with changes of relative position and orientation of the lirecontrol system and the target to enable vehicle personnel to acquirelire control system attitude for projectile-target collision. l 9. Aniall-weather projectile lire control system as set forth in claim 8wherein said coupling of said feedback circuit includes a power ampliierand a demodulator for feeding back unidirectional current signalscorresponding to. said error signals, said coupling between saidcomputer circuits and said eddy-current constrainedV gyroscope being ofsubstantially zero impedance.

References Cited by the Examiner UNITED STATES PATENTS 2,737,652 3/56White et al. 343-7 2,819,461 1/58 Bryan 343-7 3,034,116 5/62 Shelley343-7 3,044,056 7/62 Bloch 343-7.4

CHESTER L. JUSTUS, Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No3,181,147 April 27, 196

Jack A. Crawford et al.

It is hereby certified that error appears in the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

Column 13, line 8, after "adjusted" insert lead angle Signed and sealedthis 19th day of October 1965.

(SEAL) Attest:

EDWARD J. BRENNER ERNEST W. SWIDER Commissioner of Patents AttestingOfficer

1. IN AN ALL-WEATHER PROJECTILE FIRE CONTROL SYSTEM HAVING A RADARTARGET DETECTION MEANS PROVIDING ACTUAL AZIMUTH, ELEVATION, AND RANGESIGNAL INFORMATION WITH RESPECT TO A REFERENCE LINE, THE ACTUAL AZIMUTHAND ELEVATION SIGNAL INFORMATION BEING CONDUCTED THROUGH ONE CIRCUIT TOTHE DEFLECTION CIRCUIT, OF A CATHODE RAY TUBE TO PROVIDE ACTUAL AZIMUTHAND ELEVATION SIGNAL INFORMATION FOR THE CATHODE RAY TUBE CO-ORDINATEDISPLAY, AND THE RANGE SIGNAL INFORMATION TOGETHER WITH SIGNALINFORMATION REPRESENTING FACTORS AFFECTING PROJECTILE TRAJECTORY BEINGCONDUCTED TO COMPUTING CIRCUITS FOR COMPUTING SAID RANGE AND FACTORINFORMATION INTO COMPUTED RANGE, AZIMUTH, AND ELEVATION SIGNALINFORMATION WITH RESPECT TO SAID REFERENCE LINE, SAID COMPUTED RANGE,AZIMUTH, AND ELEVATION SIGNAL INFORMATION BEING APPLIED TO ANEDDY-CURRENT CONSTRAINED GYROSCOPE TO PRODUCE LEAD ANGLE AZIMUTH ANDELEVATION INFORMATION SIGNALS, SAID LEAD ANGLE AZIMUTH AND ELEVATIONALSIGNAL INFORMATION BEING APPLIIED TO SAID ONE CIRCUIT TO MODIFY SAIDACTUAL AZIMUTH AND ELEVATIONAL SIGNAL INFORMATION TO ERROR LEAD ANGLEAZIMUTH AND ELEVATION INFORMATION SIGNALS FOR CO-ORDINATE DISPLAY ON THECATHODE RAY TUBE TO SHOW THE LEAD ANGLE ERROR BETWEEN SAID REFERENCELINE AND THE TARGET, THE INVENTION WHICH COMPRISES: A FEEDBACK CIRCUITCOUPLING EACH ERROR LEAD ANGLE AZIMUTH AND ELEVATION INFORMATION SIGNALFROM POINTS IN SAID ONE CIRCUIT BETWEEN SAID APPLICATION OF SAID LEADANGLE AZIMUTH AND ELEVATION INFORMATION SIGNALS AND SAID CATHODE RAYTUBE TO POINTS IN SAID COUPLING BETWEEN SAID COMPUTER AND SAIDEDDY-CURRENT GYROSCOPE TO APPLY SAME TO THE RESPECTIVE COMPUTED AZIMUTHAND ELEVATION INFORMATION SIGNALS THEREBY ADJUSTING SAID ERROR LEADANGLE AZIMUTH AND ELEVATION INFORMATION SIGNALS TO PROVIDE INSTANTANEOUSDISPLAY ON SAID CATHODE RAY TUBE ALL RELATIVEW MOVEMENTS OF THE TARGETAND THE FIRE CONTROL SYSTEM.